Da is a semi-autobiographical, two-act play by Hugh Leonard that explores the relationship of Charlie, a successful writer, with his adoptive father, whom he calls Da (as in "Dad"). Da was first performed at the Olympia Theatre in Dublin for the Dublin Theatre Festival in 1973. In 1978, Leonard received several awards for Da, including the Antoinette Perry ("Tony") Award for best play, the New York Drama Critics' Circle Award for best play, the Drama Desk Award for outstanding new play, and the Outer Critics Circle Award for outstanding play.

Da begins in May 1968, Just after Da's funeral. As Charlie sits in the kitchen of his childhood home, sorting through his father's things, he is visited by the ghost of Da. Through a series of memory scenes, Charlie recalls key incidents in his relationship with his adoptive father throughout his life. Although as a child, Charlie is fond of Da, by the time he is a teenager, he feels ashamed of his father's ignorance and crude language. Charlie also feels disdainful of Da's subservience toward his employers and Da's hostile temper toward his wife. As an adult, Charlie is a successful writer and lives in London with his wife and children. When he is done sorting through Da's things, Charlie leaves the house, locking the door behind him, With Da's ghost inside. But, as soon as Charlie turns around, the ghost has emerged from the house and insists on following him wherever he goes.

Da explores themes of death, family, memory, and identity. As the play closes, Charlie must accept that the memory of his father cannot be locked away in the past but, for better or worse, will follow him throughout his life